test: make handling of noWarnCode stricter

This change requires all expected warnings to be specified along with
their respective code and will raise an error if the code does not
match. This also kind of fixes the behavior when the expected warning
code was noWarnCode and there is an actual warning code.

PR-URL: https://github.com/nodejs/node/pull/21075


Reviewed-By: Daniel Bevenius <daniel.bevenius@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>